The kind of motor vehicle door lock with which the invention is concerned can have a bolt system, arrangement or mechanism which is operated in response to an electrical unit which can be termed a locking system and which can have a mechanical lock cylinder operated by a mechanical key, the latter being inserted into the cylinder for rotating same.
The lock cylinder can have three functional positions, namely, an intermediate starting position, a locking-and-unlocking position to one side of the starting position and an anti-theft position to the opposite side of the starting position. Selection between these three positions is made by operation of the key.
The locking cylinder can be provided with evaluation circuitry which can detect the position of the lock cylinder by scanning or the like. The locking system can further include at lest two fixedly mounted Hall-sensor chips each of which can include a Hall-sensor transducer and the associated chip electronics such that the Hall-sensor chip can cooperate with a ferromagnetic actuating magnet operatively connected with the locking cylinder. The starting position can correspond to an intermediate zero setting with respect to the evaluation circuitry which can have a lower electric current threshold A.sub.1 and an upper electrical current threshold A.sub.2.
Door locks of this type are described, for example, in German Patent Document DE 196 34 321.6 A1 (corresponding to U.S. patent application Ser. No. 08/915,897, filed Aug. 21, 1997, Attorney's Docket No. 20465), EP 0 694 665 A 1 and German Utility Model 296 18 688.0 U1 (corresponding to U.S. patent application Ser. No. 08/950,792, filed Oct. 16, 1997, Our Docket No. 20516).
In door locks with two such Hall sensor chips, one usually selects the chips so that they are practically identical, e.g. as described in DE 94 15 257.8 U1. In that case, there must be a predetermined match between the Hall sensor and the chip electronics and the determination of that relationship can be an expensive process.
In practice, Hall sensors and Hall sensor chips as described are mass produced on an industrial scale and both the magnetic and electrical tolerances of the units can be substantial. The Hall sensor chips can be manufactured, for example, in series with fabrication tolerances which are more or less identical for a particular series. To a particular series, for example, magnetic and electronic function parameters with upper and lower limits for operability can be ascribed which will not be exceeded or below which the parameters will not fall.
However, up to now, as far as I am aware, the fact that Hall sensor chips are fabricated in such series with well defined upper and lower limits has not been utilized to overcome the drawbacks involved in selecting and matching both the magnetic and electronic components of usable Hall sensor chips for these purposes.